Human metabolism of toxic arsenic, taken up with contaminated drinking water may not be the same in all people.
A group of researchers from Mexico and the US (Arizona) have
pointed out to a gene called CYT19 in people, particularly in children,
that may be responsible for varied reactions to arsenic. The results of
their research indicate that individual genetic inheritance defines how
much the arsenic taken by the body will cause harm to the health.
In the association screening performed by the researchers for a
Mexican population, three polymorphic sites in the CYT19 gene were
significantly associated with methylation pathways for arsenic
excretion in children. Although the finding of a genetically and
developmentally restricted association with arsenic metabolism was
unexpected, the presence of a developmentally restricted component in
the metabolism of arsenic has been reported also by other researchers
(Chowdhury et al. 2003; Kurttio et al. 1998).
The research also showed that children with a mutation of the gene
variety CYT19 react to arsenic in a different manner than the adults,
namely by enhanced occurence of the dimethylated species (DMA). If, as
has been well characterized in the arsenic toxicology literature,
arsenic metabolism can govern the creation and removal of extremely
toxic arsenic species, then these findings may suggest that a
particular subset of exposed children may have increased susceptibility
to arsenic toxicity by virtue of metabolism that is skewed toward
enhanced accumulation of toxic species.
The authors conclude, that because the drinking water
concentrations of arsenic in their study represent a range that
includes a large number of children throughout the world, including
North America as well as Central and South America, the public health
and regulatory implications of this study are significant.
U.K. Chowdhury, M.M. Rahman, M.K. Sengupta, D. Lodh, C.R. Chanda, S. Roy, et al., Pattern
of excretion of arsenic compounds [arsenite, arsenate, MMA(V), DMA(V)]
in urine of children compared to adults from an arsenic exposed area in
Bangladesh, J. Environ. Sci. Health A 38(1) (2003) 87-113.